Pen drive for telescribing apparatus



24, 1965 A. J. SPARLING 3,203,001

PEN'DRIVE FOR TELESGRIBING APPARATUS Filed Oct. 25, 1961 surface.

United States Patent 0 bra-.5

3,203,001 PEN DRIVE FOR TELESQRHBHNG APPARATUS Arthnrl. Sparling, Manhattan Beach, Qalifi, assignor to Los Angeles, (Calif, a cor- This invention relates to telescribers and, more particularly, is concerned with an improved linkage system for driving the pen in a telescriber receiver.

In conventional telescribing equipment, handwritten messages are transmitted by electrical means and reproduced at a receiver. The equipment generally involves some type of mechanical linkage between the writing stylus and a pair of transducers which generate electrical signals corresponding to two components of position of the writing stylus. At a receiver, a corresponding lin age drives a pen from two transducers which change the received electrical signals into two components of position at the receiver.

In order to obtain faithful reproduction at the receiver in response to the electrical signals derived from the transmitter, it is desirable that the mass of the linkage system controlling the pen be as small as practical. This is necessary so that the high acceleration rates required to reproduce ordinary handwriting may be produced by relatively small low power transducers. This permits both the weight and the cost of the receiver units to be maintained at a minimum.

It has been the practice heretofore to construct the linkagefwhether it be in the form of a W-linkage or a pantograph type linkage between the two drive motors and the pen element, of thin flexible rods. The inherent springiness of the rods permitted up and down movement of the pen required to lift the pen off the surface of the writing paper, such as required between words, and for dotting is and crossing ts. It also permitted the pen to move vertically with slight undulations in the writing Linkages of this type have been limited in the past to use with very light pen pressures. Wet ink pen systems have been used for this reason. It has long been recognized that it would be desirable to be able to produce carbon copies of a transcribed message, which is not possible with the wet ink pen. Moreover, the wet ink pen system has long been recognized as a source of expense and annoyance in operation. It has therefore been proposed that a ball-point pen system be used for the two fold purpose of avoiding the problems with the wet ink pen system and at the same time providing a means for producing carbon copies, since the ball-point pen may be operated at greater surface pressures than the wet ink pen system. However, the ball-point pen requires pressures of the order of 60 grams in contrast to wet ink pen pressures previously used of the order of two grams. Pressures of this magnitude impose additional load problems on the linkage and the drive system of existing telescriber units which, until the present invention, have not successfuly been solved.

A pantograph drive or a W-linkage drive essentially provides a cantilever support of the pen element from the drive shafts of two positioning motors. One obvious Way of increasing the pen pressure is to increase the stiffness of the linkage rods. However, this makes it very difiicult to maintain a constant pressure over the entire writing surface, since the increased Stiffness in effect increases the spring rate of the linkage. Thus any warping or skewing of the writing surface or lack of exact parallel'relationship between the drive shafts connected to the linkage results in a substantial change in pressure over the Writing surface. The expense of maintaining dfiddfifil Patented Aug. 24, 1965 adequate tolerances to accommodate a high spring rate is prohibitive.

An alternative is to provide a linkage of thin rods having a low spring rate with the writing force being produced by increased deflection, i.e., pre-loading, of the supporting linkage. However, the lower spring rate of the linkage system results in a support linkage which is not sufliciently stifi to accurately move the pen against the increased friction drag resulting from a ball-point pen at high pen pressures.

The present invention provides a low mass linkage systern for driving a pen from a pair of positioning motors. The linkage is preferably arranged in a W-linkage configuration, but the invention may be incorporated in a pantograph type of linkage. The invention provides high pen pressure with a stiff driving linkage between the pen and motors to enable the pen to follow the motor movements with extreme accuracy. At the same time, the linkage provides resilient support to permit vertical movement of the pen, the resilient support nevertheless having a low spring rate so that vertical movement of the pen does not materially change the force pressing the pen against the paper.

In brief, the present invention provides a linkage system in a telescriber receiver including first and second rotatable drive shafts positioned on either side of a recording strip of paper or the like. The linkage includes first and second drive arms of rigid hollow tubular shape secured respectively at one end in cantilever fashion to the first and second drive shafts. The free ends of the drive arms are movable in an are parallel to and above the surface of the recording strip but in rigidly spaced relation thereto. First and second rigid hollow tubular pen support arms are pivotally joined to each other and are respectively joined to the first and second drive arms by first and second universal joints. Each universal joint provides relative movement between the pen support arm and the associated drive arm about two mutually perpendicular axes lying in a plane perpendicular to the surface of the paper. A coil spring having a low spring rate is positioned inside each of the tubular pen support arms with one end of the spring connecting through the universal joint to the associated drive arm at a point slightly off one of the pivotal axes of the universal joint, whereby the spring causes the pen support arm to pivot in a direction to press the pen against the paper strip.

For a more complete understanding of the invention, reference should be made to the accompanying drawing, wherein:

FIGURE 1 is an elevational view of an embodiment of the invention in a W-linkage;

FIGURE 2 is a partial sectional view taken on the line 2-2 of FIGURE 1; and

FIGURE 3 is a partial sectional view taken on the line 3-3 of FIGURE 1.

Referring to the drawings in detail, the numerals 1t) and 12 indicate a pair of vertical drive shafts which may extend from a pair of motors or other suitable rotary drive means associated with a telescribing receiver such as described in detail in Patent No. 2,355,087. The angular positions of the drive shafts It and 12 are controlled by electrical signals received from a transmitting device in a manner which is described in the above-mentioned patent but the details of which form no part of the present I invention.

The present invention is directed to an improved linkage as shown in the drawings for interconnecting the two drive shafts 10 and 12 with a ball-point writing element, indicated generally at 14, which normally engages a strip of writing material, indicated at 16, supported in plane and positioned between the drive shafts 1d and 12. Rota- ,3 tion of the drive shafts iii and 12 moves the pen 14 over the surface of the writing paper 16 to provide a visual trace corresponding to the handwriting of the person manipulating a stylus at a transmitting station (not shown). Each of the shafts is journalled in suitable bearings to provide rotational support of the shafts from the frame of the machine. This is shown in FIGURE 2, in

- which the shaft rotates in a bearing indicated at '17,

the bearing being supported from the frame of the machine as indicated at 19.

The linkage comprises a first drive arm in the form of a thin walled tube 18. Asshown in FIGURE 2, one end of the tube is provided with a solid plug 20 and is pressed or otherwise secured in an opening in a hub 22. The hub 22 fits over the end er the shaft 10 and is secured to the shaft by a set screw 24. Thus the drive arm 18 is supported in cantilever fashion from the drive shaft M with its longitudinal axis extending at right angles to the axis of rotation of the shaft 10. i The hollow tubular shape of the drive arm 18 provides maximum rigidity with a minimum of weight.

The drive arm 18 is joined to a pen support arm 26, also made of hollow tubing, through a universal joint connection, indicated generally at 28. The universal joint 28, as best shown in FIGURE 2, includes a clevis member which is pressed or otherwise secured in the free end of the drive arm 18. The clevis member 3t) receives a pin 32 which is supported by the clevis for rotation about a vertical axis. To reduce friction, the pin 32 may be journalled in ball bearings 34 and 36 mounted in the clevis member 30. Thus the pin 32 is easily rotated about a vertical axis. v

The end 33 of the pen support arm 26 adjoining the universal joint 28 is provided with a pivot member 38, a portion of which is pressed or otherwise secured in the hollow end 33 of the arm 26. The pivot member 38 is provided with a pivot support portion 46 which extends around the upper end of the pin 32. A hinge pin 42 extends through the pivot support dfi and through the upper end of the pin 32 to provide a pivotal connection therebetween having a hinge axis which extends at right angles to the rotary axisof the pin 32. The support arm 26 being tubular is extremely rigid in relation to its weight.

A similar drive arm 44 and pen support arm 46v of hollow tubular material are joined by a universal joint48 which is identical to the universal joint 28. The drive arm 44 is supported from the drive shaft 12 by a hub 50 similar to the hub 22.

The two pen support arms 26 and 46 are pivotally joined in the manner best shown in FIGURE 3. The pen support arm 26 is terminated in a flat hinge member 52 which is pressed or otherwise secured in the end of the tubular portion of the arm 26. A hinge pin 54 is pressed in an opening in the member 52 and is journalled in a frictionlessball bearingfid supported by the arm 46. An end-plug member 53 is inserted in the open end of the tubular portion of the arm 46 and is countersunk to receive the ball bearing 56 which is located in a position to receive the hinge pin 54 for rotation about a vertical'axis. The end-plug 58 provides a mounting for the ball-point pen 14- which may be secured in position by means of a strap 60 secured in any suitable manner to the mounting portion of the plug member 58. a In order to exert a downward force of the ball-point pen against the writing surface 16, each of the universal joints 2 8 and 48 has associated therewith a coil spring such as indicated at 62 in FIGURE 2. The coil springs 62 are positioned inside the respective tubular arms 26 and 46. One end of the spring 62 is provided with a hook which extends around the vertical pin 32 between the bearings 34 and 36 within the clevis member 30. The other end of the spring 62 is secured to an adjustable anchor member 64 slidably positioned within the respective tubular arms 26 and 4-6. These arms are provided with elongated slots, such as indicated at 66, through which a' clamping screw 63 extends. The screw 68 threadably engages the anchor member 64 so as to clamp it in any longitudinal position along the length of the slot 66. In this way, the loading tension on the spring 62 can be adjusted to provide the proper writing pressure on the ball-point pen 14.

It will be noted that the spring 62 operates on a fulcrum point below the horizontal axis of the hinge pin 42 thus producing a downward force on the ball-point pen 14. The coil spring with its relatively low spring rate combinedwith the short fulcrum distance between the position of the spring and the hinge axis 42 combine to permit relatively large vertical deflection of the ball-point pen 14 without any material change inthe downward force applied to the ball-point pen 14.

From the above description, it will be recognized that a relatively lightweight cantilever linkage is provided for driving a'ball-point pen from a pair of rotary drive shafts. The linkage is extremely rigid in relation to its weight and thus permits highly accurate positioning of the pen in spite of increased drag forces which are imposed by the use of a ball-point pen operating with substantial pen pressure gainst the writing surface. The spring arrangement provides for uniform pressure at the pen regardless of the up and down movements it may experience in passing over the surface of the writing paper. Thus the linkage system provides for a relaxing of tolerances which otherwise might be required in the manufacture of such equipment.

What is claimed is 1. In a telescriber in which a visual record is traced on a recording strip, the combination comprising first and second rotatable shafts positioned on either side of the strip, first and second drive arms of rigid tubular shape secured rigidly at one end respectively to the first and sec-, ond drive shafts, each drive arm being supported at one end in cantilever fashion and projecting across a portion of the strip perpendicularly to the rotational axis of the associated drive shaft, whereby the free ends of the arms are movable in an are parallel to and above the surface of the recording strip but in rigidly spaced relation thereto, first and second rigid tubular pen support arms, the pen support arms being pivotally joined to each other with the pivotal axis extending at right angles to the surface of the record strip, first and second universal joints respectively connecting one of the ends of the first and second support arms to the free ends of the first and second drive arms, each universal joint providing relative movement between the pen support arm and the associated drive arm about two perpendicular axes, one axis being horizontal to therecording strip and the other axis being perpendicular to the recordingstrip, and first and second coil springs having a low spring rate positioned inside the tubular pen support arms, one end of each spring being anchored to the pen support arm and the other end being anchored to the associated drive arm at the vertical pivot 'axis but below the horizontal pivot axis of the universal oint.

2. In a telescriber in which a visual record is traced on a recording strip, the combination comprising first and second rotatable shafts positioned on either side of the strip, first and second drive arms of rigid tubular shape secured rigidly at one endrespectively to the first and second drive shafts,-eacl1 drive arm being supported at one end in cantilever fashion and projecting across a portion of the strip perpendicularly to the rotational axis of the associated drive shaft, whereby the free ends of the arms are movable in an arc parallel to and above the surface of the recording strip but in rigidly spaced relation thereto, first and second rigid tubular pen support arms, the pen support arms being pivotally joined to each other with the pivotal axis extending at right angles to the surface of the record strip, first and second universal joints end drive arms, each universal joint providing relative movement between the pen support arm and the associated drive arm about two perpendicular axes, one axis being horizontal to the recording strip and the other axis being perpendicular to the recording strip, and spring means having a low spring rate associated with the respective universal joints for urging the pen support arms to pivot about the horizontal axes of the universal joints, whereby pressure is applied between the pen and recording strip.

'3. In a telescriber in which a visual record is traced on a recording strip, the combination comprising first and second rotatable shafts positioned on either side of the strip, first and second drive arms secured rigidly at one end respectively to the first and second drive shafts, each drive arm being supported at one end in cantilever fashion and projecting across a portion of the strip perpendicularly to the rotational axis of the associated drive shaft, whereby the free ends of the arms are movable in an are parallel to and above the surface of the recording strip but in rigidly spaced relation thereto, first and second rigid pen support arms, the pen support arms being pivotally joined to each other with the pivotal axis extending at right angles to the surface of the record strip, first and second universal joints respectively connecting one of the ends of the first and second support arms to the free ends of the first and second drive arms, each universal joint providing relative movement between the pen support arm and the associated drive arm about two perpendicular axes, one axis being horizontal to the recording strip and the other axis being perpendicular to the recording strip, and spring means having a low spring rate associated with the respective universal joints for urging the pen support arms to pivot about the horizontal axes of the universal joints, whereby pressure is applied between the pen and recording strip.

4. In a telescriber in which a visual record is traced on a recording strip, the combination comprising first and second drive arms, each drive arm being pivotally supported at one end in cantilever fashion and projecting across a portion of the strip, first and second rigid pen support arms, the pen support arms being pivotally joined to each other with the pivotal axis extending at right angles to the surface of the record st-rip, first and second universal joints respectively connecting one of the ends of the first and second support arms to the free ends of the first and second drive arms, each universal joint providing relative movement between the pen support arm and the associated drive arm about two perpendicular axes, one axis being horizontal to the recording strip and the other axis being perpendicular to the recording strip, and a coil spring having a low spring rate positioned inside one of the tubular pen support arms, one end of the spring being anchored to the pen support arm and the other end being anchored to the associated drive arm at the vertical pivot axis but below the horizontal pivot axis of the universal joint.

5. In a telescriber in which a visual record is traced on a recording strip, the combination comprising first and second drive arms, each drive arm being pivotally supported at one end in cantilever fashion and projecting across a portion of the strip, first and second rigid pen support arms, the pen support arms being pivotally joined to each other with the pivotal axis extending at right angles to the surface of the record strip, first and second universal joints respectively connecting one of the ends of the first and second support arms to the free ends of the first and second drive arms, each universal joint providing relative movement between the pen support arm and the associated drive arm about two perpendicular axes, one axis being horizontal to the recording strip and the other axis being perpendicular to the recording strip, a recording pen, means coupling the ends of the pen support arms remote from the universal joints to the recording pen, and spring means having a low spring rate associated with at least one of the respective universal joints for urging the associated pen support arm to pivot about the horizontal axis of the associated universal joint, whereby pressure is applied between the pen and recording strip.

6. A telescriber unit comprising means defining a writing surface, a ball-point pen, first and second rigid pen support arms, means for pivotally joining the pen support arms adjacent one end, means for securing the pen to said one end of one of the pen support arms, first and second rigid drive arms, first and second universal joints coupling one end of each of the drive arms to the respective pen support arms, means for pivotally supporting at fixed points with respect to the writing surface means each of the drive arms at the opposite ends thereof from the universal joints, and spring means connected between one drive arm and the associated support arm, said spring means acting through the universal joint coupling the one drive arm to the associated pen arm to urge the pen support arms to pivot about the universal joints in a direction toward the writing surface, whereby the ballpoint pen is pressed against the writing surface.

References Cited by the Examiner UNITED STATES PATENTS 1,438,829 12/22 Howell 346139 2,332,511 10/43 Glassman 346-139 X 2,420,633 5/47 Wittel et a1 346l39 X LEYLAND M. MARTIN, Primary Examiner. JULIA E. COINER, Examiner. 

1. IN A TELESCRIBER IN WHICH A VISUAL RECORD IS TRACED ON A RECORDING STRIP, THE COMBINATION COMPRISING FIRST AND SECOND ROTATABLE SHAFTS POSITIONED ON EITHER SIDE OF THE STRIP, FIRST AND SECOND DRIVE ARMS OF RIGID TUBULAR SHAPE SECURED RIGIDLY AT ONE END RESPECTIVELY TO THE FIRST AND SECOND DRIVE SHAFTS, EACH DRIVE ARM BEING SUPPORTED AT ONE END IN CANTILEVER FASHION AND PROJECTING ACROSS A PORTION OF THE STRIP PERPENDICULARLY TO THE ROTATIONAL AXIS OF THE ASSOCIATED DRIVE SHAFT, WHERBY THE FREE ENDS OF THE ARMS AREMOVABLE IN AN ARC PARALLEL TO AND ABOVE THE SURFACE OF THE RECORDING STRIP BUT IN RIGIDLY SPACED RELATION THERETO, FIRST AND SECOND RIGID TUBULAR PEN SUPPORT ARMS THE PEN PITOTAL AXIS EXTENDING AT RIGHT ANGLES TO THE SURFACE THE PIVOTAL AXIS EXTENDING AT RIGHT ANGLES TO THE SURFACE OF THE RECORD STRIP, FIRST AND SECOND UNIVERSAL JOINTS RESPECTIVELY CONNECTING ONE OF THE ENDS OF THE FIRST AND SEC OND SUPPORT ARMS TO THE FREE ENDS OF THE FIRS AND SECOND DRIVE ARMS, EACH UNIVERSAL JOINT PORVIDING RELATIVE MOVEMENT BETWEEN THE PEN SUPPORT ARMS, ONE END OF EACH SPRING BEING DRIVE ARM ABOUT TWO PERPENDICULAR AXES, ONE AXIS BEING HORIZONTAL TO THE RECORDING STRIP AN THE OTHER AXIS BEING PERPENDICULAR TO THE RECORDING STRIP, AND FIRST AND SECOND COIL SPRINGS HAVING A LOW SPRING RATE POSITIONED INSIDE THE TUBULAR PEN SUPPORT ARMS, ONE END OF EACH SPRING BEING ANCHORED TO THE PEN SUPPORT ARM AND THE OTHER END BEING ANCHORED TO THE ASSOCIATED DIRVEA RM AT THE VERTICAL PIVOT AXIS BUT BELOW THE HORIZONTAL PIVOT AXIS OF THE UNIVERSAL JOINT. 